Anomalous optical behavior in pyramid-like indium oxide (In₂O₃) nanostructures

We present the VLS synthesis and photoluminescence characteristics of In₂ O₃ nanopyramids at different growth temperatures in oxygen deficient environment. TEM images showed preferential growth of [2 2 2] planes. XPS results confirmed oxygen vacancies and metallic indium, which affected the Raman modes and reduced the correlation length. The PL spectrum consisted a very strong band in visible region was resolved in two sub-bands centered at 622 nm and 668 nm corresponding to oxygen vacancies and indium interstitials, respectively. Temperature dependent PL behavior was normal in nanostructures grown at 875 °C and 760 °C, with activation energies of 6.60 meV and 5.02 meV, 6.69 meV and 4.26 meV for the two bands, respectively. A Berthelot-like PL response was observed in nanostructures grown at 830 °C, with escape energy of 4.12 meV and 0.53 meV and activation energy of 2.09 meV and 5.33 meV for the two bands, respectively.